Sustained Depolarization of the Resting Membrane Potential Regulates Muscle Progenitor Cell Growth and Maintains Stem Cell Properties In Vitro.

It is important to maintain the myogenic properties of muscle progenitor cells (MPCs) during in vitro expansion for stem cell therapies and tissue engineering applications. Controlling cell fate for biomedical interventions will require insight on all aspects that influence cellular properties. The resting membrane potential (Vmem) has proven to be a key parameter involved in cell proliferation, migration and differentiation. This current work is focused on elucidating the impact of sustained depolarization on MPC growth and differentiation in vitro. Cultures were treated with either potassium gluconate or the sodium-potassium pump blocker ouabain and evaluated for proliferation, DNA content using propidum iodide staining, and differentiation. Cell proliferation measurements showed a modest stimulatory effect at certain concentration ranges for each agent, but higher concentrations of potassium gluconate strongly inhibited growth in a dose dependent manner. Cell cycle analysis with flow cytometry demonstrated an increase in the number of cells in S phase, but increasing concentrations of potassium gluconate arrested cells at G1. Immunostaining, Western blot analysis and light microscopy revealed that potassium gluconate exposure delayed cell fusion and maintained a higher population of cells expressing the muscle stem cell marker Pax7. The impairment on cell fusion was transient and myotube formation recovered after the treatments were removed. Taken together, this work suggests that transmembrane voltage gradients can be used as a powerful regulator of MPC properties in vitro. Examination of how these physiological parameters modulate cell behavior will reveal a new set of tools that can be capitalized on in tissue engineering and regenerative medicine.